Question

改错 1.tom`s mother is taller than my 2.both she and her sisther is doing their homework

Answer 1

1.Tom's mother is taller than mine.
my改为mine, 比较级同级比较，Tom's mother和my mother比较，为了避免重复单词mother，改为名词性物主代词mine=my mother.
2.Both she and her sisther are doing their homework.
both...and...作主语，谓语动词用复数，is改为are

Answer 2

1. Tom's mother is taller than mine.用名词性物主代词，mine 相当于my mother
2. both表示两个都，后面的谓语动词应该跟复数，所以用are，变成
Both she and her sister are doing their homework.

Answer 3

1.Tom's mother is taller than mine.
my改为mine, 比较级同级比较，Tom's mother和my mother比较，为了避免重复单词mother，改为名词性物主代词mine=my mother.
2.改为：Both her sister and she are doing their homework.一般排序时，要先把别人排在前面。